Concrete slab key-joint forming member



Jan. 10, 1961 w. D. WILBUR CONCRETE sum KEY-JOINT FORMING MEMBEROriginal Filed Jan. 11, 1957 INVENTOR WARREN D. WILBUR JVQQ Q ATTORNEYReissued Jan. 10, 1961 CONCRETE SLAB KEY-JOINT FORNIING MEMBER Warren D.Wilbur, 13379 Pastel Lane, Mountain View,

Calif., assignor of one-half to Richard N. Tone, Belmont, Calif.

Original No. 2,848,929, dated Aug. 26, 1958, Ser. No. 633,723, Jan. 11,1957. Application for reissue Sept. 3, 1959, Ser. No. 838,011

7 Claims. (CI. 94-47) Matter enclosed in heavy brackets [II appears inthe original patent but forms no part of this reissue specification;matter printed in italics indicates the additions made by reissue.

This invention relates to a concrete slab key joint forming member andhas for an object to provide an approved key-joint forming member foruse in concrete slab construction such as roadway paving, air fieldrunways, building floors, and elsewhere wherever large slabs of concretemay be poured to form a uniform road, runway or floor surface.

A further object of this invention is to provide an approved concreteslab key-joint forming member which can be fabricated at a minimumexpense which may be made of any suitable material, including sheetmetal or extruded metal or plastic, wherein the metal may be sheet ironor sheet aluminum or may be extruded aluminum, or any other suitablemetal or material.

A further object of this invention is to provide a key-joint formingmember for use between adjacent slabs of poured concrete so that theconcrete will automatically form a key-joint with the adjacent slab, andwherein a small wire or a large rod dowel may be placed in positionthrough the member of this invention so as to provide a suitableexpansion joint between adjacent slabs of concrete.

Still a further object of this invention is to provide a key-jointforming member or concrete slab construction which greatly reduces thecost of concrete slabs, which enables slabs of concrete to be pouredsimultaneously on both sides of the key-joint forming member of thisinvention, and at the same time provides a clean permanent cold orcontraction straight line joint between adjacent slabs of concrete, thuspreventing random cracking in the slab.

Still a further object of this invention is to provide a key-jointforming member which may be placed in operative position veryinexpensively by merely hanging it over appropriate positioned stakeswhereupon the concrete slab may be poured first on the side of themember which is away from its supporting stake, and may immediately andcontinuously be poured on the other side of the forming member withoutWaiting for the first slab to harden.

Still a further object of this invention is to provide a key-jointforming member for concrete slabs wherein the forming member has aninverted U or inverted J hook at its upper end defining a downwardlyopening socket which will hang over appropriately positioned stakesdriven into the ground and thus be automatically positioned in theproper location ready for the concrete slab to be poured thereagainstand thereaftaer be poured on the other side thereof leaving the formpermanently in position and providing a sharp and definite dividing edgebetween adjacent slabs.

Still a further object of this invention is to provide an approvedkey-joint forming member for concrete slabs which if desired may be usedin cooperation with wood forms for temporary use and then be strippedaway thereafter, but which preferably will be used with metal supportingstakes appropriately located whereupon the forming member of thisinvention may be quickly and readily positioned thereon at a substantiallabor cost over the use of wooden forms, forming a permanent boundaryfor the slab construction at a substantially lower cost than is providedby old time methods of providing temporary wooden forms or wood.supported forms.

Still a further object of this invention is to provide a key-jointforming member for concrete slabs which will form a V-notch extendinginto the side between the upper and lower surfaces of a concrete slabinto which V notch the poured concrete of the next adjacent slab willenter and which may be poured without waiting for the first slab toharden. I

Formerly large concrete slabs were poured in achecker board formation,making up each individual square of approximately 25 feet with woodenforms, then first pouring the concrete in alternate squares of thechecker board which are non-contacting and waiting for such squares toharden, then stripping away the form and then pouring intermediatesquares between the previously formed squares. With this invention, itis not necessary to provide the wooden forms at such great expense,instead, as when pouring a 5 in. slab, steel stakes about /a in. thickby 1 in. wide are placed along the boundaries of the proposed squares bybeing driven into the ground until they extend at the proper height,just 5 inches above the properly prepared ground level. Then, thekey-joint forming member of this invention is placed in position bymerely suspending the inverted U or J hook integrally formed along itsupper edge over the metal stakes, the overall height of a key-jointforming member for a five inch slab being 4 /2 inches so that the bottomedge is supported /2 inch above the ground level. Wire dowels or splicewires are inserted through appropriately spaced openings through thejoint forming member so as to extend over the wire reinforcing gridnormally placed in the concrete slab within the square before theconcrete is poured. These wire dowels thus serve to substantially tiethe wire reinforcing grids of adjacent squares together. If instead anexpansion joint is to be formed as in road paving, then larger sizeddowels made possibly of iron rods may be inserted through appropriatelypositioned apertures in the forming member, with one end of the rodgreased so that the concrete at that end will not adhere thereto thuspermitting expansion and contraction between adjacent squares of theslab, yet maintaining them on the same level.

With the foregoing and other objects in view, as will hereinafter becomeapparent, this invention comprises the construction, combination andarrangment of parts hereinafter set forth, disclosed, claimed and shownin the accompanying drawings wherein:

Fig. 1 is a section view through adjoining edges of a pair of concreteslab sections with the key-joint forming member of this invention inplace therebetween.

Fig. 2 is a perspective view of the key-joint forming member of thisinvention.

Fig. 3 is an end view of the key-joint forming member of this inventionin Operative position, ready for the concrete slab to be poured onopposite sides thereof.

There is shown at 10 the concrete slab key-joint forming member of thisinvention. As shown in Fig. 2, this key-joint forming member may be madeof any suitable material, such as sheet metal or sheet material, thesheet material being any suitable material such as plastic or othersuitable material having sutficient strength. It may be fabricated bymaking appropriate folds from a strip of sheet metal or sheet material,or it may be fabricated by extruding it in the finished shape ifdesired. The member 10 as fabricated comprises a lower plane portion 12and an upper plane portion 14 integrally secured together'by the twoangular intermediate portions 16 and 18 forming a V extending to oneside of the plane of the portions 12 and 14. Inasmuch as these portions12 and 14 will in operation be placed vertically, these portions willhereinafter be referred to as vertically extending plane portions,portion 12 being the lower vertical portion and portion 14 being theupper vertically extending portion. The angular intermediate portion 18extends integrally up from the upper edge of the lower verticallyextending portion 12, and similarly the upper angular intermediateportion 16 extends downwardly fro-m the lower edge of the uppervertically extending plane portion 14, and meets the other angularportion 18 at a V apex 20, thereby forming a longitudinally extendingconcavo convex portion providing keyed interfitting tongue and grooveportions in the parting faces of the adjacent slab sections.

Either before or after forming the portions into their V apex, twoseries of suitably spaced apertures 22 and 24 may be formedtherethrough. At the same time, a series of suitably spaced apertures 26is provided in the lower vertically extending plane portion 12 and asimilar series of apertures 28 is provided in the upper verticallyextending portion 14. The purpose of these several series of apertures22, 24, 26 and 28 will become apparent hereinafter.

The upper end of the upper vertically extending portion 29 is foldedover at right angles as at 30 extending in a horizontal direction fromthe vertical portion opposite to the direction of the V apex 20 andforms a sharp right angle with the vertically extending portion 14. Thena portion 32 is folded downwardly from the portion 30, the portion 30extending horizontally in relation to the vertically extending portion14, and the downwardly extending portion 32 extends at a sharp rightangle to the horizontally extending portion 30, so that the downwardlyextending portion 32 is parallel with the vertically extending portion14. Then the extreme end portion 34 of the downwardly extending portion32 is flared outwardly at a slight degree as shown whereby the portions30, 32 and 34 form an inverted U or an inverted J hook relative to theplane of the vertically extending portions.

Obviously, the concrete slab key-joint forming member 10 of thisinvention will be made in as many suitable sizes as is necessaryaccording to the thickness of the concrete slab with which it is to beused. The dimensions will naturally be proportional to the particularthickness of the slab, but it will now be described for use inconnection with a concrete slab 36 and 38 which will be inches inthickness. In such case, the overall height of the fabricated key-jointforming member of this invention will be 4 inches between the horizontalportion 30 and the lower edge 40 of the lower vertically extendingportion 12. In utilizing this member, a series of preferably flattenedstakes, of'metal, such as iron, will be placed along a surveyed linedefining the edge of the slab 36 to he poured, these stakes 42 beingdriven into the ground 44 to a suitable depth with their upper ends setto grade so that just '5 inches of the stake 42 will extend above thelevel 46 of the supporting ground 44.

.Then, the member 10 will be supported by merely placing its flaredinverted U or J hook end over the upper end of the series of alignedstakes -42, whereupon the horizontal portion 30 will be supported atgrade elevation the exact height corresponding to the thickness of theslab 36 to be poured.

Next, if [a key-joint] reinforcement is to be provided between adjacentslabs 36 and 38 to be poured, a series of wire dowels or splice wires43, approximately 12 inches in length will be inserted through thespaced apart small apertures 22 in the V apex '20. As seen in Fig. 3,these dowels 48 will extend over the adjacent wire grid portions 50. Inthe particular size of slab above discussed, these wire grids 50 aremade usually of No. 10 guage wire grids and in such case, the wiredowels or splice wires 48 are of No. 9 guage. The wire grids 50 aresupported in the customary manner before the concrete is pouredthereover. Inasmuch as the key-joint forming member 10 of this inventionis supported on a series of stakes 42 merely by its own weight, withoutthe necessity of tying or fastening the member thereto, the concreteslab 36 on the [male or tongue] female or groove side of the V apex 42will first be poured thereby of course pressing the member 10 againstits supporting stakes 42. As soon as the slab 36 has been poured, theslab 38 may be poured immediately without waiting for the slab 36 toharden, thereby, of course, enabling a continuous process of pouringconcrete to take place. As the concrete slab 38 is poured, it will, ofcourse, flow into the [female] male or tongue side of the V apex 20 asat 52, and, of course, will flow up under the hollow provided by theinverted U or J hook at the upper end of the upper vertically extendingportion 14. The stakes extend across (span) the concave side of themember so that the concrete forming the tongue 52 of the key flowsaround and interlocks with the stakes. Ensuing curing and shrinking ofthe concrete slabs thus eflects a controlled parting of the sections ina straight line crack at the convex side of the member.

The wire dowel receiving and supporting apertures 22 are about A of aninch spaced apart at 6 inch centers starting at 3 inches from each endof the member 10.

After the concrete is poured, it may be smoothed or leveled immediately,the levelling rod being moved back and forthover the horizontal surface30 which in pouring may be temporarily covered with concrete. The rodsas conventional will be long enough to extend over the horizontalsurfaces 30 at both ends of the slab thereby levelling the slab evenwith the surface of the horizontal portion 30 and thus providing a cleanedge to the concrete when it contracts away therefrom after it hassolidified.

If an expansion joint is to be provided, the series of large holes 24 atthe V apex 20 is utilized by placing rod dowels therethroughapproximately /2 inch or so in diameter, the apertures 24 beingapproximately of an inch in diameter so that the rod dowels may extendeasily therethrough. As customary, these dowels may be 24 inches inlength, one-half thereof being covered with a coating of grease beforethe concrete is poured thereover. In this manner, the rod dowel issecurely fastened in one slab and slidably received in the other slabthereby providing an expansion joint yet maintaining both slabs at thesame level in the customary manner.

The apertures 26 and 28 have been provided for use as nail holes, suchapertures being A; inch in diameter on a 24 inch center starting fro-meach end of the member 10. These nail holes are provided for use in thecase where the contractor may desire to utilize wooden stakes or woodforms for any reason, in which case the nail holes are already there fornailing the member 10 to the wooden forms for either temporary orpermanent use as may be desired.

However, when the member 10 is merely to be used as a form betweenadjacent slabs, the wire dowels 48 may be used to splice the customarywire grids or mesh together in adjacent slabs 36 and 38.

[There has thus been provided by this invention a key-joint formingmember for use in forming adjacent concrete slabs which may be pouredsuccessively without delay, without waiting for one slab to hardenbefore the next slab is poured, which forms a key-joint between theslabs with a V apex extending from one slab 38 as at 52 into theadjacent slab 36. The cost of materials and of labor in utilizing thisform as a key-joint forming member between adjacent slabs provides asubstantial saving, as much as a labor saving of 90% over utilizingconventional method of wood forms. Although in some cases the form maybe stripped away, particularly where the adjacent slab is not poureduntil the previous slab has hardened, it probably will be less expensiveto leave the form in position permanently and pour adjacent slabscontinuously without taking time for the first poured slab to harden]There has thus been provided by this invention a combination andco-functioning of all of the following features:

(a) The provision of a low-cost expendable form for pouring adjacentsections of a concrete slab wherein the device functions as a form forsupporting the concrete of both slabs, and the top of the deviceprovides a straight line screed for finishing the top surfaces of theadjacent sections flush with the screeding edge and with each other, and

(b) The adjacent sections may be monolithically poured by pouring firstthe slab section at the side away from the stake and then immediatelypouring the slab section at the other side in a continuous operation,and

(c) The joint is keyed with interfitting tongue and groove portion inthe parting faces of the adjacent slab sections thereby permittingrelative expansion and contraction of the sections while beingmaintained in a vertically interlocked condition, and

(d) The form is readily positioned with substantial savings in labor byfirst driving a plurality of stakes at spaced-apart intervals along thelength of the joint with their upper ends set to grade, and then merelymounting the downwardly opening socket of the form member in supportedposition on the upper ends of the stakes so that the upper edge of theform member will be automatically supported at grade elevation, and

(e) The stakes are embedded in the tongue portion of the keyed joint soas to efiect a straight line controlled parting of the adjacent sectionsat the convex side of the member.

Although this invention has been described in considerably detail, suchdescription is intended as being illustrative rather than limiting,since the invention may be variously embodied, and the scope of theinvention is to be determined as claimed.

Having thus set forth and disclosed the nature of this invention, whatis claimed is:

l. A combination form and contraction joint for adjacent slab sectionsof a monolithically poured concrete slab comprising a plurality ofexpendable flattened stakes set to grade at spaced apart alignedintervals, in combination with an expendable relatively rigid sheetmaterial member comprising a vertically extending plane portion havingan inverted J -hook at the top edge thereof, said inverted J-hookconsisting of a horizontal portion extending at a right angle from thetop edge of said vertical plane portion and terminating in a downwardlyextending vertical portion of considerably less height than that of saidvertical plane portion, said inverted J-hook snugly embracing and being[solely] supported at grade level on the upper ends of said flattenedstakes with the vertically extending plane portions of said sheet memberheld in contact with the adjacent vertical portions of said stakes,whereby, when concrete is poured against said sheet material on the sideaway from said stakes, it will press said sheet material member againstsaid supporting stakes, and concrete may then be poured immediatelyagainst the stake supporting side of said sheet material member.

2. The combination joint means of claim 1, at least 6 the bottom portionof said downwardly extending portion of said ,inverted J-hook flaringoutwardly away therefrom.

3. The combination joint means of claim 1, and a deflected key portionextending integrally from said vertically extending plane portion ofsaid sheet material member in the opposite direction from said invertedJ-hook.

4. The combination joint means of claim 3, said sheet material memberhaving upper and lower plane portions in the same vertical plane, saiddeflected key portion extending longitudinally of said sheet materialmember intermediate said upper and lower plane portions.

5. The combination joint means of claim 4, said deflected key portionhaving side portions angularly offset from said vertical plane portionsof said sheet material member.

6. The combination joint means of claim 5, said deflected key portionbeing V-shaped.

7. A combination form and key contraction joint for adjacent slabsections of a monolithically poured concrete slab comprising, aplurality of expendable ground stakes having their upper ends set tograde at spacedapart intervals along the length of the joint, and anelongated expendable relatively rigid sheet member providing the partingfaces between said adjacent sections and being formed with alongitudinally extending concavo-convex portion providing keyedinterfitting tongue and groove portions in said parting faces and beingof inverted J-hook form providing a longitudinally extending invertedU-shaped top portion defining a downwardly opening socket at the concaveside of said member receiving and being supported upon and snuglyembracing said upper ends of said stakes and being supported thereby ina straight line and with the upper surface of said top portion at gradeelevation thereby functioning as a screed for finishing the top surfacesof said sections flush with said edge and with each other, a lowerportion of said member connected to and depending from saidconcavo-convex portion and adapted to be laterally supported by saidstake whereby when concrete is poured against said member on the convexside away from said stake it will press said member against said stakeand concrete may then be poured immediately against the opposite concaveside of said member, said stakes traversing said concave side of saidmember for embedding in said tongue portion to thereby secure theconcrete to said concave side and efiect controlled parting of saidsections at said convex side of said member.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS 271,582 McKnight Jan. 30, 1883 1,591,509 BrookmanJuly 6, 1926 1,607,690 Rue Nov. 23, 1926 1,741,585 Robertson Dec. 31,1929 1,769,828 Fischer July 1, 1930 1,770,359 Fischer July 8, 19301,804,215 Fischer May 5, 1931 1,939,007 Heltzel Dec. 12, 1933 1,963,088Heltzel June 19. 1934 2,023,472 Heltzel Dec. 10, 1935 2,027,516 BurrellJan. 14, 1936 2,374,623 Sale Apr. 24, 1945 2,630,892 Hammitt et a1 Mar.10, 1953 2,779,280 Strange Jan. 29, 1957

